Transforming growth factor (TGF)-beta-1 but not plasminogen activator inhibitor (PAI)-I can induce a burst of PAI-I production in normal human bronchial epithelial (NHBE) cells or in T antigen- transformed normal human bronchial epithelial cells. These cells do not normally produce this gene product. However, tumorigenic, ras-transfected, T antigen transformed NHBE cells constitutively produce PAI-I. Mesothelioma cells, but not normal human mesothelial cells, produce platelet-derived growth factor (PDGF)-A chain protein which is biologically active in receptor binding assays. However, compared to the normal cells the mesothelioma cell lines do not respond to the mitogenic signals of PDGF. Normal mesothelial cells produce mRNA for basic fibroblast growth factor (FGF). Some mesotheliomas, but no normal mesothelial cells, produce TGF-alpha, while all classes of human mesothelial cells are negative for epidermal growth factor (EGF) production.